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Issue:ISSN 1006-5539
          CN 51-1183/TE

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    Your Position ：Home->Past Journals Catalog->2015 Vol.5

    Influence of Normalizing Temperature on Microstructure and Mechanical Properties of Controlled Rolling Steel for Preparation of Manifolds
    Author of the article:Liu Yinglai, Wang Gaofeng, Nie Xianghui, Xu Yan
    Author's Workplace：CNPC Tubular Goods Research Institute
    Key Words：Controlled rolling steel; Microstructure of manifolds; Low valley range of strength
    Abstract：Under laboratory conditions, used is a box-type heater to stimulate the effect of heating process on the material near branch pipes of manifolds at oil and gas pipeline stations and analyzed is the change rule of microstructure and mechanical properties of four compositions of materials containing such three kinds of steel grades as X60, X70 and X80 after being tempered at 650 °C and results from stimulation and analysis show that after the materials containing such three kinds of steel grades as X60, X70 and X80 are heated and have heat preservation in different temperature conditions between 300 °C and 1050 °C and then tempered at 650 °C , their microstructures in lower than the Austenite transition temperature present the morphology of tempered bainite and a small amount of ferrite. When the raw materials are heated above the temperature of phase change, their microstructure will be transformed into coarsening ferrite and a small amount of pearlite. After heating, the yield strength and hardness of the materials present a trend of rise, drop and rise again along with the increase of heating temperature. All of the selected materials have a low valley of strength in the 700 °C to 1000 °C heating temperature conditions and the minimum yield strength dropped 94 - 212 MPa than the measured value of the raw material, far lower than that of the raw material. The Charpy impact energy absorption of the materials drops along with the increase of heating temperature. Although the testing results obtained in -20 °C temperature condition still can meet the requirement of engineering design, the dispersion of energy absorption values in high temperature zone is obvicusly increased than that of the raw material.


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